The known methods of manufacturing of electrodes with a polymer coating are mainly based on the chemical polymerization method, such as the ones described in U.S. Pat. Nos. 4,999,263, 6,533,918, U.S. patent application No. 20020089807A1, which implies the formation of a polymer layer on a conducting substrate placed into an electrolytic bath with electrolyte-containing polymer compounds. Different polymer coatings are formed on the conducting substrate depending on the electrolytes used for this purpose.
Both purely organic systems and polymer metal complexes (or organometallic compounds) fall into the category of the redox polymers [H. G. Cassidy and K. A. Kun. Oxidation Reduction Polymer//Redox Polymers. Wiley—Interscience, New York, 1965]. Polymers that contain a metal usually offer better conductivity.
Redox polymers produced from the octahedral source complex compounds are known. Polypyridine complexes of the composition poly-[Me(v-bpy)x(L)y], where: Me=Co, Fe, Ru, Os; L=v-bpy (4-vinyl-4′-methyl-2,2′-bipyridine), phenanthroline-5,6-dione, 4-methylphenanthroline, 5-aminophenanthroline, 5-chlorophenanthroline (x+y=3) [Hurrel H. C., Abruna H. D. Redox Conduction in Electropolymerized Films of Transition Metal Complexes of Os, Ru, Fe, and Co//Inorganic Chemistry. 1990. V. 29. P. 736-741], as well as porphyrin and phthalocianine metal complexes and electrodes modified by these complexes [U.S. Pat. Nos. 5,729,427, 5,840,443] may serve as examples of such redox polymers. However, the above-named polymers are characterized by poor energy-accumulating properties and are not used for the production of electrodes for energy-storage devices.
Polymer metal complexes based on the substituted tetra-dentate Schiff's bases, including poly-[Me(R-Salen)] (where Me—a transition metal having at least two different degrees of oxidation—e.g. Ni, Pd; Co, Cu, Fe; Salen—a residue of bis-(salicylaldehyde)-ethylenediamine in Schiff's base, R—electron-donating substituent—e.g. radicals CH3O—, C2H5O—, HO—, —CH3 and others), are known [Timonov A. M., Shagisultanova G. A., Popeko I. E. Polymeric Partially-Oxidized Complexes of Nickel, Palladium and Platinum with Schiff Bases//Workshop on Platinum Chemistry. Fundamental and Applied Aspects. Italy, Ferrara, 1991. P. 28]. The above-named polymer complexes were produced via the electrochemical oxidation of square-planar monomers [Me(R-Salen)], and the stack structure of a polymer was confirmed through the use of spectral methods.
Known (from publications) studies of metal complexes poly-[Me(R-Salen)] and electrodes chemically modified by these metal complexes conducted by the inventors of the present invention and other researchers were of theoretical nature. They were directed at the identification of structure and electrochemical behavior of these polymers. Exclusively analytical chemistry and optics were considered as a fields of potential application of these polymers, such as in U.S. Pat. Nos. 6,323,309, 5,543,326, and 5,840,443.
Moreover, many researchers working in this field believe that poly-[Me(R-Salen)] are formed due to the covalent bonds between the phenyl nuclei of monomers, and not due to the formation of the stack structures-[P. Audebert, P. Capdevielle, M. Maumy. Redox and Conducting Polymers based on Salen-Type Metal Units; Electrochemical Study and Some Characteristics//New J. Chem. 1992. V. 16. P. 697], which, in turn, according to their opinion, makes it impossible to use poly-[Me(R-Salen)] as an energy-accumulating substance in energy-storage devices.
However, that negative attitude toward the redox polymers (as an energy-accumulating layer) is more likely caused by specific features of the formation of the redox polymer layer on a conducting substrate and, at the end, by the structure of the formed layer (rather than by electrochemical properties of the redox polymer itself). Conventional methods of electro-polymerization (which imply the supply of a constant voltage to a substrate) don't allow to produce the electrodes offering a high specific energy capacity. As the inventors believe, this is associated with the fact that, with the stack structure of the redox polymer layer being formed in the mode of continuous polymerization, defects (e.g. individual stacks—redox polymer fragments that for different reasons have stopped growing in the process of redox polymer layer formation) are produced in the layer being formed. If, for example, the process of the redox polymer layer formation is conducted on a porous substrate (which is associated with the desire to obtain a larger specific surface of the polymer layer), then continuous polymerization results in the quick overgrowth of the outer surface of the substrate with a polymer, while its inner developed surface stays uncovered with a polymer.
The engineering problem addressed by the present invention comprises the development of a method of manufacture of electrodes chemically modified by a redox polymer that offer a high specific energy capacity, making it possible to utilize these electrodes in energy-storage devices.